Memory device

ABSTRACT

A memory device is provided. The memory device includes a cell array having a plurality of cells, each of the plurality of cells operative to store a bit value. The memory device further includes a reset circuit connected to the cell array. The reset circuit is operative to reset, in parallel, the bit value stored in each of the plurality of cells to a predetermined bit value.

BACKGROUND

A common type of integrated circuit memory is a static random accessmemory (SRAM) device. A typical SRAM memory device has an array ofmemory cells. The memory cell uses six transistors connected between anupper reference potential and a lower reference potential (typicallyground) such that one of two storage nodes can be occupied by theinformation to be stored, with the complementary information stored atthe other storage node.

Power gating and voltage retention techniques are commonly implementedto the memory array to reduce power consumption. For example, powergates may be used to turn off memory periphery items in a deep sleepmode, and both the periphery items and the memory array in a shut downmode. Generally, an on-chip SRAM retains some of the bit values storedin the SRAM when it comes out of power down mode or shut down mode. Thismay be a security risk as the content may be readable by maliciousprograms. Moreover, some applications need to start a SRAM with all thebit values set to value zero. For example, an application may need tostart with a clear SRAM and set individual bits.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a block diagram illustrating an example memory device inaccordance with some embodiments.

FIG. 2 is a diagram illustrating an example cell array in accordancewith some embodiments.

FIG. 3A is a diagram illustrating a memory device with a reset circuitin accordance with some embodiments.

FIG. 3B is a diagram illustrating a memory device with another resetcircuit in accordance with some embodiments.

FIG. 3C is a diagram illustrating a memory device with multiplesub-blocks in accordance with some embodiments

FIG. 4 illustrates timing diagrams of a reset circuit in accordance withsome embodiments.

FIG. 5 is a flow diagram illustrating a method for resetting a memorydevice in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

FIG. 1 discloses a block diagram of an example memory device 100 inaccordance with some embodiments. Memory device 100 can be a randomaccess memory, such as a static random access memory (SRAM) device. Asshown in FIG. 1, memory device 100 includes at least one cell array 110,as well as a plurality of peripheral circuits such as a decoder circuit120, a local input/output (TO) circuit 130, a local control circuit 140,a global IO circuit 150, a global control circuit 160, a power controlcircuit 170, and a reset circuit 180. Memory device 100 may furtherinclude other components not shown in FIG. 1. In example embodiments,memory device 100 can be part of an integrated circuit (IC) chip.

Cell array 110 includes a plurality of memory cells (also referred to asplurality of bitcells) arranged in a matrix of m rows and n columns.Each of the plurality of cells of cell array 110 is operative to storeone bit of information (that is, 0 or 1). The plurality of cells of cellarray 110 are accessed through a plurality of word lines and a pluralityof bit line pairs. Cell array 110 is discussed in greater detail withreference to FIG. 2. Although memory device 100 is shown to include onlyone cell array 110 for ease of discussion, memory device 100 couldinclude multiple cell arrays 110.

The peripheral devices include circuits that provide various functionsof memory device 100 associated with cell array 110. For instance,decoder circuit 120 of memory device 100 is operative to decode one ormore address lines to select a word line (WL) of cell array 110 andcharge the selected word line to a logic high. The logic high isapproximately equal to a first predefined potential. In exampleembodiments, decoder circuit 120 includes a plurality of logic operatorsto decode potentials on the address lines to identify a word line to beactivated. The address lines are charged to a logic high (that is,approximately equal to the first predetermined potential) or to a logiclow (that is, approximately equal to a second predetermined potential).In example embodiments, the second predetermined potential isapproximately equal to the ground potential or zero volts. In someembodiments, a number of output lines of decoder circuit 120 is equal toa number of rows of cell array 110, each of the outputs being associatedwith a word line of a row.

Local 10 circuit 130 of memory device 100 is operative to read and writedata from and into cell array 110. For example, local IO circuit 130 isoperative to sense potentials at the plurality of bit line pairs andcompare the potentials for each pair. In example embodiments, when thepotential of a first bit line is more than the potential of a second bitline of a bit line pair, local IO circuit 130 reads the output to be abit value 1. In addition, when the potential of a first bit line is lessthan the potential of the second bit line of the bit line pair, local IOcircuit 130 reads the output to be a bit value 0.

Local control circuit 140 of memory device 100 is operative to controllocal IO circuit 130. For example, local control circuit 140 isoperative to configure local IO circuit 130 in a read mode to readinformation from cell array 110 or in a write mode to write informationinto cell array 110. In addition, local control circuit 140 is operativeto enable local IO circuit 130 in a hold mode where no data is read fromor written into cell array 110.

Global TO circuit 150 of memory device 100 is operative to combineinput/output from local TO circuits 130. For example, memory device 100may include multiple cell arrays 110 each having a respective local TOcircuit 130. Global TO circuit 150 is operative to combine theinformation from multiple local TO circuits 130 into a global TO circuit150 of memory device 100. For example, local TO circuits 130 areoperable to store output from cell arrays 110 in a shift register,global TO circuit 150 is operable to read the data from the shiftregister, and provide the data as the output of memory device 100.

Global control circuit 160 of memory device 100 is operative to controlglobal IO circuit 150. For example, global control circuit 160 isoperative to configure global IO circuit 150 to select one or more localIO circuits 130 to read data from or write data into. In anotherexample, global control circuit 160 is operative to configure a readingsequence for global IO circuit 150 to read data from, or a writingsequence to write data into one or more local IO circuits 130.

Power control circuit 170 is operative to control and manage power forone or more components of memory device 100. For example, power controlcircuit 170 is operative to selectively connect one or more componentsof memory device 100 to a voltage terminal in some embodiments. Powercontrol circuit 170 includes a plurality of logic gates or power gates.Each of the plurality of power gates is operative to power up or powerdown an associated component of memory device 100. For example, powercontrol circuit 170 is operative to generate a shut down (SD) signal toshut down all components of memory device 100. In addition, powercontrol circuit 170 is operative to generate a deep sleep low power(DSLP) signal to shut down one or more peripheral circuit to reducepower consumption of memory device 100. Moreover, power control circuit170 is operative to generate a ready (RDY) signal to indicate loweringup of memory device 100.

Reset circuit 180 is operative to reset the stored values in each of theplurality of cells of cell array 110 to a predetermined value. Forexample, reset circuit 180 is operative to reset the stored values ineach of the plurality of cells of cell array 110 to a bit value 0 or toa bit value 1. Reset circuit 180 is discussed in greater detail withreference to FIG. 3 of the disclosure.

FIG. 2 illustrates an example cell array 110 in accordance with someembodiments. As shown in in FIG. 2, cell array 110 includes a pluralityof cells designated as 202 a 1, 202 a 2, . . . , 202 mn. Each cell ofcell array 110 is operable to store one bit (that is, 0 or 1) ofinformation. An example cell includes a pair of cross-coupled invertors(also referred to as Q and Q-bar—where Q-bar is complementary to Q) tostore the one bit of information. The cross coupled invertors areconnected to pair of access transistors which grant access to theinformation stored in the cross-coupled invertors. In exampleembodiments, cells of cell array 110 may be formed using fourtransistors, six transistors, or eight transistors. In addition, memorycells of cell array 110 can be single port cells or multi-port (such as,two port and three port) cells.

Continuing with FIG. 2, the plurality of memory cells of cell array 110are arranged in a matrix of a plurality of rows (that is, m rows) and aplurality of columns (that is, n columns). Each of the m rows of cellarray 110 include a first plurality of cells and each of the n columnsof cell array 110 include a second plurality of cells. A number of rowsand a number of columns of cell array 110 may depend on a size of cellarray 110. For example, for a 32 kilo bit size, cell array 110 mayinclude 256 rows and 128 columns.

For example, and as shown in FIG. 2, a first row of cell array 110includes a first plurality of cells designated as 202 a 1, 202 a 2, . .. , 202 an. And each row may continue to the m^(th) row of cell array110 which includes the first plurality of cells designated as 202 m 1,202 m 2, . . . , and 202 mn. Similarly, a first column of cell array 110includes a second plurality of cells designated as 202 a 1, . . . , 202m 1. Moreover, a second column of cell array includes the secondplurality of cells designated as 202 a 2, . . . , 202 m 2. And eachcolumn may continue to the n^(th) column which includes the secondplurality of cells designated as 202 an, . . . , and 202 mn.

Each of the first plurality of cells of the first row is connected to afirst word line designated as WL1. Each row may continue to the m^(th)row where each of the first plurality of cells is connected to a wordline designated as WLm. Word lines WL1, WLm control access to therespective cells. For example, WL1 controls access to cells 202 a 1, 202a 2, . . . , and 202 an. That is, to read or write data to cells 202 a1, 202 a 2, . . . , and 202 an, WL1 is charged to logic 1. To hold datain cells 202 a 1, 202 a 2, . . . , and 202 an, WL1 is charged to logic0.

Continuing with FIG. 2, the second plurality of cells in each column ofcell array 110 are connected to a bit line pair. For example, the secondplurality of cells of the first column designated as 2 a 1, . . . , 2 m1 are connected to a first bit line pair (that is, a first bit line BL0and a second bit line BLB0). Similarly, the second plurality of cells ofthe second column designated as 2 a 2, . . . , 2 m 2 are connected to asecond bit line pair (that is, a first bit line BL1 and a second bitline BLB1). And each column may continue to the n^(th) column whereinthe second plurality of cells designated as 202 an, . . . , and 202 mnare connected to a nth bit line pair (that is, a first bit line BLn anda second bit line BLBn). In example embodiments, each of second bitlines BLB0, BLB1, . . . , BLBn are complimentary to a corresponding oneof first lines BL0, BL1, . . . , BLBn of bit line pairs. The bit linepairs are used for reading or writing data to a cell.

The word lines WL1, . . . , WLm are connected to gates of the pair ofaccess transistors of associated cells. Therefore, when a word line isactivated and charged to logic 1 (that is, charged to the firstpredetermined potential), the respective cells are connected to one bitline of the bit line pair. The associated cells are then accessed bycomparing a potential difference between bit lines of the bit line pair

In some embodiments, power gating and voltage retention techniques areimplemented in the memory array to reduce power consumption. Forexample, power gates may be used to turn off memory periphery items in adeep sleep mode, and both the periphery items and the memory array in ashut down mode. An SRAM may retain some of the stored bit values when itcomes out of power down mode or shut down mode. This may be a securityrisk as the content may be readable by malicious programs. Moreover,some applications need to start a SRAM with all the bit values set tovalue zero. For example, an application may need to start with a clearSRAM and set individual bits. SRAMs usually do not provide a means toreset the content to zero on shutdown. One way to reset the content isto write zero at each corresponding address of the SRAM per cycle. Thus,to clear a SRAM with 1024 addresses may need 1024 cycles, for example.If there are multiple SRAM blocks, each block may need to be cleared.Hence, it may take too long (that is, too many cycles) to clear all SRAMblocks. In accordance with aspects of the present disclosure, a resetcircuit is included to clear SRAM blocks efficiently and quickly.

FIG. 3A is a partial block diagram and a partial circuit diagramillustrating memory device 100 with a reset circuit, for example, resetcircuit 180, in accordance with some embodiments. Reset circuit 180 caninclude, in some examples, a reset signal generator circuit 302, aplurality of bias circuits 304 (for example, a first bias circuit 304 a,a second bias circuit 304 b, . . . a nth bias circuit 304 n), and aplurality of restoration circuit (that is, a first restoration circuit308 a, . . . , a mth restoration circuit 308 m). Other configurationsand components of reset circuit 180 are within the scope of thedisclosure. For example, and as shown in FIG. 3A, memory device 100includes reset signal generator circuit 302 and a plurality of biascircuits 304, that is, a first bias circuit 304 a, a second bias circuit304 b, . . . , and a nth bias circuit 304 n. Each of plurality of biascircuits 304 is associated with a column of memory device 100. Forexample, first bias circuit 304 a is associated with the first column,second bias circuit 304 b is associated with the second column,continuing to nth bias circuit 304 n which is associated with the nthcolumn.

In example embodiments, reset signal generator circuit 302 is operativeto generate a reset signal, also referred to as a clear all (designatedas CLRall) signal. As shown in FIG. 3A, reset signal generator circuit302 implements logical disjunction of the SD signal and the RDY signal.For example, reset signal generator circuit 302 includes an OR logicgate 306. The SD signal is provided to a first input of OR logic gate306 and the RDY signal is provided to a second input of OR logic gate306. The CLRall signal is received at the output of OR logic gate 306.Hence, when both the SD signal and the RDY signal are at a logic low,the CLRall signal is also at a logic low. If one of the SD signal andthe RDY signal is at a logic high, the CRLall signal is also at a logichigh.

Each of plurality of bias circuits 304 is operative to set the bit linepairs of the associated column to a desired signal level. For example,plurality of bias circuits 304 is operative to set the first bit linesBL0, BL1, . . . , BLn of the associated bit line pair to a logic low andthe second bit lines BLB0, BLB1, . . . , BLBn of the associated bit linepair to a logic high.

In example embodiments, each of plurality of bias circuits 304 mayinclude a plurality of transistors and an invertor. For example, firstbias circuit 304 a includes a first transistor 312 a 1, a secondtransistor 312 a 2, and an invertor 312 a 3. Similarly, second biascircuit 304 b includes a first transistor 312 b 1, a second transistor312 b 2, and an invertor 312 b 3, continuing to nth bias circuit 304 nwhich includes a first transistor 312 n 1, a second transistor 312 n 2,and an invertor 312 n 3. First transistors 312 a 1, 312 b 1, . . . , 312n 1 of plurality of bias circuits 304 are also referred to as pull downtransistors and may include NMOS transistors. However, other types oftransistors are within scope of the disclosure. Second transistors 312 a2, 312 b 2, . . . , 312 n 2 of plurality of bias circuits 304 are alsoreferred to as pull up transistors and may include PMOS transistors.However, other types of transistors are within scope of the disclosure.Invertors 312 a 3, 312 b 3, . . . , 312 n 3 of plurality of biascircuits 304 may include NOT logic gates. However, other types of logicgates are within scope of the disclosure.

A source/drain of each of first transistors 312 a 1, 312 b 1, . . . ,312 n 1 of plurality of bias circuits 304 is connected to one of thefirst bit lines BL0, BL1, . . . , BLn of a corresponding column. Inaddition, a drain/source of each of first transistors 312 a 1, 312 b 1,. . . , 312 n 1 of plurality of bias circuits 304 is connected to asecond potential (that is, the ground). A gate of each of firsttransistors 312 a 1, 312 b 1, . . . , 312 n 1 of plurality of biascircuits 304 is connected to an output of a corresponding one ofinvertors 312 a 3, 312 b 3, . . . , 312 n 3 of plurality of biascircuits 304.

A source/drain of each of second transistors 312 a 2, 312 b 2, . . . ,312 n 2 of plurality of bias circuits 304 is connected to one of thesecond bit lines BLB0, BLB1, . . . , BLBn of a corresponding column. Inaddition, a drain/source of each of second transistors 312 a 2, 312 b 2,. . . , 312 n 2 of plurality of bias circuits 304 is connected to afirst potential (that is, the VCC). A gate of each of second transistors312 a 2, 312 b 2, . . . , 312 n 2 of plurality of bias circuits 304 isconnected to the output of reset signal generator circuit 302. Moreover,the output of reset signal generator circuit 302 is connected to gatesof each of first transistors 312 a 1, 312 b 1, . . . , 312 n 1 and to aninput of each of invertors 312 a 3, 312 b 3, . . . , 312 n 3.

Second transistors 312 a 2, 312 b 2, . . . , 312 n 2 are operative tocharge the second bit line of each of the plurality of columns of cellarray 110 to a logic high in response to the CLRall signal being at alogic low. Invertors 312 a 3, 312 b 3, . . . , 312 n 3 are operative toinvert the CLRall signal and provide the inverted CRLall signal to acorresponding one of first transistors 312 a 1, 312 b 1, . . . , 312 n1. The inverted CLRall signal causes the first bit line of each of theplurality of columns of cell array 110 to be charged to logic low whenthe CLRall signal is at logic low.

In addition, the output of reset signal generator circuit 302 isconnected to each of word lines WL1, . . . , WLm of cell array 110 via aplurality of restoration circuits. For example, the output of resetsignal generator circuit 302 is connected the first word line WL1 via afirst restoration circuit 308 a, continuing to the mth word line WLmwhich is connected to the output of reset signal generator circuit 302is connected via mth restoration circuit 308 m.

Each of plurality of restoration circuits 308 a, . . . , 308 m areoperative to charge a corresponding one of the word lines WL1, . . . ,WLm of cell array 110 to a logic high when triggered via the CLRallsignal. Each of plurality of restoration circuits 308 a, . . . , 308 mincludes a first logic gate and a second logic gate. For example, firstrestoration circuit 308 a includes a first logic gate (that is, a NOTlogic gate 314 a) and a second logic gate (that is NAND logic gate 310a), continuing to the mth restoration circuit 308 m which includes afirst logic gate (that is, a NOT logic gate 314 m) and a second logicgate (that is NAND logic gate 310 m). An input of each of NOT logicgates 314 a, . . . , 314 m is connected to a corresponding output ofdecoder circuit 120. An output of each of NOT logic gates 314 a, . . . ,314 m is connected to a first input of a corresponding one of NAND logicgates 310 a, . . . , 310 m. The output of reset signal generator circuit302 is connected to a second input of each of NAND logic gates 310 a, .. . , 310 m. An output of each of NAND logic gates 310 a, . . . , 310 mis connected to a corresponding one of word lines WL1, . . . , WLm.

The output of reset signal generator circuit 302 is connected to gatesof each of second transistors 312 a 2, 312 b 2, . . . , 312 n 2 ofplurality of bias circuit 304. In addition, the output of reset signalgenerator circuit 302 is connected to an input of each of invertors 312a 3, 312 b 3, . . . , 312 n 3 of plurality of bias circuit 304. Eachinvertors 312 a 3, 312 b 3, . . . , 312 n 3 is operative to invert theCRLall signal. An output of each of invertors 312 a 3, 312 b 3, . . . ,312 n 3 is connected to a gate of a corresponding one of secondtransistors 312 a 2, 312 b 2, . . . , 312 n 2. In addition, an providingthe inverted CLRall signal to second transistors 312 a 2, 312 b 2, . . ., 312 n 2 of plurality of bias circuit 304.

In operation, each of plurality of restoration circuits 308 a, . . . ,308 m is operative to charge a corresponding one of the word lines WL1,. . . , WLm to a logic high when both a decoder 120 signal and theCLRall signal is at a logic low at the corresponding one of the wordlines WL1, . . . , WLm. For example, when output of decoder 120 is at alogic low and the CLRall signal is also at a logic low, the output ofeach of plurality of restoration circuits 308 a, . . . , 308 m is at alogic high, thereby charging each of word lines WL1, . . . , WLm to alogic high. Moreover, each of plurality of bias circuits 304 isoperative to charge first bit lines BL0, BL1, . . . , BLn to a logic lowand the second bit lines BLB0, BLB1, . . . , BLBn to a logic high whenthe CLRall signal is at a logic low. Hence, by charging each of the wordlines WL1, . . . , WLm to a logic high, a bit value of zero is forcedwritten in each of plurality of cells of cell array 110 in parallel bycharging the first bit lines BL0, BL1, . . . , BLn to a logic low andthe second bit lines BLB0, BLB1, . . . , BLBn to a logic high. That is,for the “reset” operation, a first node (that is, a Q node) of across-coupled invertor of each of the plurality of cells is set at a bitvalue of 0 and a complementary second node (that is, a Q node) of thecross-coupled invertor of each of the plurality of cells is set at a bitvalue of 1.

In example embodiments, cell array 110 of memory device 100 may be resetby writing a bit value of one in each of the plurality of cells. Suchreset is also referred to as a set operation, as each of the pluralityof cells is written over or “set” with a bit value of one. In exampleembodiments, a bit value of one in each of the plurality of cells may bewritten by charging the first bit lines BL0, BL1, . . . , BLn to a logichigh and the second bit lines B1B0, BLB1, . . . , BLBn to a logic low.For example, for “set” operation, the first node (that is, the Q node)of the cross-coupled invertor of each of the plurality of cells is setat a bit value of 1 and the complementary second node (that is, the Qnode) of the cross-coupled invertor of each of the plurality of cells isset at a bit value of 0.

FIG. 3B illustrates memory device 100 with another reset circuit whichis operative to reset cell array 110 by writing a bit value of one ineach of the plurality of cells. Reset circuit 180 of memory device 100of FIG. 3B includes a reset signal generator circuit 302 and a pluralityof bias circuits 320, that is, a first bias circuit 320 a, a second biascircuit 320 b, . . . , and a nth bias circuit 320 n. Each of pluralityof bias circuits 320 is associated with a column of memory device 100.For example, first bias circuit 320 a is associated with the firstcolumn, second bias circuit 320 b is associated with the second column,continuing to nth bias circuit 320 n which is associated with the nthcolumn. Plurality of bias circuits 320 are operative to set the firstbit lines BL0, BL1, . . . , BLn of the associated bit line pair to alogic high and the second bit lines BLB0, BLB1, . . . , BLBn of theassociated bit line pair to a logic low.

In example embodiments, each of plurality of bias circuits 320 mayinclude a plurality of transistors and an invertor. For example, firstbias circuit 320 a includes a first transistor 322 a 1, a secondtransistor 322 a 2, and an invertor 322 a 3. Similarly, second biascircuit 320 b includes a first transistor 322 b 1, a second transistor322 b 2, and an invertor 322 b 3, continuing to nth bias circuit 320 nwhich includes a first transistor 322 n 1, a second transistor 322 n 2,and an invertor 322 n 3. First transistors 322 a 1, 322 b 1, . . . , 322n 1 of plurality of bias circuits 320 are also referred to as pull uptransistors and may include PMOS transistors. However, other types oftransistors are within scope of the disclosure. Second transistors 322 a2, 322 b 2, . . . , 322 n 2 of plurality of bias circuits 320 are alsoreferred to as pull down transistors and may include NMOS transistors.However, other types of transistors are within scope of the disclosure.Invertors 322 a 3, 322 b 3, . . . , 322 n 3 of plurality of biascircuits 320 may include NOT logic gates. However, other types of logicgates are within scope of the disclosure.

A source/drain of each of first transistors 322 a 1, 322 b 1, . . . ,322 n 1 of plurality of bias circuits 320 is connected to one of thefirst bit lines BL0, BL1, . . . , BLn of a corresponding column. Inaddition, a drain/source of each of first transistors 322 a 1, 322 b 1,. . . , 322 n 1 of plurality of bias circuits 320 is connected to afirst potential (that is, the VDD). A gate of each of first transistors322 a 1, 322 b 1, . . . , 322 n 1 of plurality of bias circuits 320 isconnected to an input of a corresponding one of invertors 322 a 3, 322 b3, . . . , 322 n 3 of plurality of bias circuits 320. In addition, agate of each of first transistors 322 a 1, 322 b 1, . . . , 322 n 1 ofplurality of bias circuits 320 is connected to the output of resetsignal generator circuit 302. Moreover, the output of reset signalgenerator circuit 302 is connected to an input of each of invertors 322a 3, 322 b 3, 322 n 3.

A source/drain of each of second transistors 322 a 2, 322 b 2, . . . ,322 n 2 of plurality of bias circuits 320 is connected to one of thesecond bit lines BLB0, BLB1, . . . , BLBn of a corresponding column. Inaddition, a drain/source of each of second transistors 322 a 2, 322 b 2,. . . , 322 n 2 of plurality of bias circuits 320 is connected to asecond potential (that is, the ground). A gate of each of secondtransistors 322 a 2, 322 b 2, . . . , 322 n 2 is connected to an outputof each of invertors 322 a 3, 322 b 3, . . . 322 n 3.

First transistors 322 a 1, 322 b 1, . . . , 322 n 1 are operative tocharge the first bit line of each of the plurality of columns of cellarray 110 to a logic high in response to a reset signal (which is alsoreferred to as a SETall signal for the set operation) being at a logiclow. Invertors 322 a 3, 322 b 3, . . . , 322 n 3 are operative to invertthe SETall signal and provide the inverted SETall signal to a gate of acorresponding one of second transistors 322 a 2, 322 b 2, . . . , 322 n2. The inverted SETall signal causes the second bit line of each of theplurality of columns of cell array 110 to be charged to logic high whenthe SETall signal is at logic low.

In operation, reset signal generator circuit 302 is operative togenerate the SETall signal which is at a logic low when both the SDsignal and the RDY signal are at a logic low. Each of plurality ofrestoration circuits 308 a, . . . , 308 m is operative to charge acorresponding one of the word lines WL1, . . . , WLm to a logic highwhen both decoder 120 signal and the SETall signal is at a logic low forthe one of the word lines WL1, . . . , WLm. Moreover, each of pluralityof bias circuits 320 is operative to charge first bit lines BL0, BL1, .. . , BLn to a logic high and the second bit lines BLB0, BLB1, . . . ,BLBn to a logic low when the SETall signal is at a logic low. Bycharging each of the word lines WL1, . . . , WLm to a logic high, a bitvalue of one is forced written in each of plurality of cells of cellarray 110 in parallel by charging the first bit lines BL0, BL1, . . . ,BLn to a logic high and the second bit lines BLB0, BLB1, . . . , BLBn toa logic low. That is, for the “set” operation, the first node (that is,the Q node) of the cross-coupled invertor of each of the plurality ofcells is set at a bit value of 1 and the complementary second node (thatis, the Q node) of the cross-coupled invertor of each of the pluralityof cells is set at a bit value of 0.

In FIG. 3B, each memory cell of the cell array 110 may be written or“reset” with a logical low value by reset by writing a bit value of zeroin each of the plurality of cells. In example embodiments, a bit valueof zero in each of the plurality of cells may be written by charging thefirst bit lines BL0, BL1, . . . , BLn to a logic low and the second bitlines B1B0, BLB1, . . . , BLBn to a logic high. That is, for the “reset”operation, the first node (that is, the Q node) of the cross-coupledinvertor of each of the plurality of cells is set at a bit value of 0and the complementary second node (that is, the Q node) of thecross-coupled invertor of each of the plurality of cells is set at a bitvalue of 1.

In example embodiments, when a number of the plurality of cells in cellarray 110 is more than a predetermining number, the plurality of cellsare segmented into sub-blocks for re-setting. For example, when thenumber of the plurality of cells in cell array 110 is more than 64 kthen, the plurality of cells are segmented into more than onesub-blocks, each of the sub-blocks having less than or equal to 64 kcells. In addition, when a number of columns is more than apredetermined number, then the plurality of cells are partitioned intomultiple sub-blocks each containing less than or equal to thepredetermined number of columns. Similarly, when a number of rows ismore than a predetermined number, then the plurality of cells arepartitioned into multiple sub-blocks each containing less than or equalthe predetermined number of rows.

FIG. 3C illustrates an example memory device with multiple sub-blocks inaccordance with some embodiments. As shown in FIG. 3C, memory device 100includes a plurality of sub-blocks (350 a, . . . , 350 n). Each of theplurality of sub-blocks may include up to a predetermined number ofcells, columns, or rows. The plurality of cells in the sub-blocks arereset using a corresponding (that is, a dedicated) reset circuit(designated as 180 a, . . . , 180 n). For example, the plurality ofcells of a first sub-block 350 a is reset using a first reset circuit180 a continuing to a plurality of cells of a nth sub-block 350 n whichis reset using a nth reset circuit 180 n. In example embodiments, afinite state machine 360 is provided to the co-ordinate re-setting ofplurality of sub-blocks 350 a, . . . , 350 n. For example, finite statemachine 360 may determine that a plurality of cells of first sub-block350 a have been reset and triggers resetting of a next sub-blockcontinuing to nth sub-block 350 n. In other examples, finite statemachine 360 is implemented as a counter which is incremented by a value1 after resetting of a sub-block tallying up to a total number ofsub-blocks of cell array 110 of memory device 100.

FIG. 4 illustrates a timing diagram 400 for memory device 100 inaccordance with some embodiments. For example, FIG. 4 illustrates timingdiagrams of the SD signal (designated as 404), the RDY signal(designated as 406), and the CLRall signal (designated as 408). As shownin the timing diagram 400, during a shut down duration (designated as410) the SD signal is at a logic high. There is no power supply tomemory device 100 during the shut down duration. In addition, during theshut down duration, the RDY signal is at a logic low indicating thatmemory device 100 is not ready for access.

The ending of shut down duration begins with the DSLP signal changingfrom a logic high to a logic low. The DSLP signal changing from a logiclow to a logic low triggers powering up of the peripheral components ofmemory device 100. For example, the DSLP signal changing to a logic lowtriggers powering up of decoder circuit 120, local input/output (TO)circuit 130, local control circuit 140, global IO circuit 150, globalcontrol circuit 160, power control circuit 170, and reset circuit 180.

After a first predetermined duration from when the DSLP signal changesto a logic low, the SD signal also changes from a logic high to a logiclow. The changing of the SD signal from a logic high to a logic low alsomarks beginning of a power up duration (designated as 412). The firstpredetermined duration between changing of the DSLP signal and the SDsignal is determined as a time sufficient to power up the peripheralcomponent of memory device 100. The changing of SD signal to a logic lowtriggers powering up of cell array 110 of memory device 100.

In addition, and as shown in FIG. 4, at the end of the power up process(or the end of shut down process), the SD signal changes to a logic lowwhich results in the CLRall signal to change from a logic high to alogic low. The CLRall signal changing to a logic low triggers resettingof the plurality of cells of cell array 110 with a predetermined bitvalue. The CLRall signal remains at a logic low for the power upduration. The power up duration is determined as a time sufficient toreset each of the plurality of cells of cell array 110 to apredetermined bit value. At the end of the power up duration, the RDYsignal changes from a logic low to a logic high indicating that memorydevice 100 is ready for access. The changing of the RDY signal causesthe CLRall signal to change to a logic high thereby turning off firsttransistors 412 a 1, 412 b 1, . . . , 412 n 1 and second transistors 412a 2, 412 b 2, . . . , 412 n 2.

FIG. 5 is a flow diagram of a method 500 for resetting a memory devicein accordance with some embodiments. Steps of method 500 may be storedas instructions which may be executed by a processor to implement method500. At block 510 of method 500, a reset signal as a logical disjunctionof a first signal (that is, the SD signal) indicating an initiation of apower up duration of a plurality of cells and a second signal (that is,the RDY signal) indicating a completion of the power up duration of theplurality of cells of memory device 100 is generated. The plurality ofcells of memory device 100 are arranged in a matrix of a plurality ofrows and a plurality of columns, wherein each of the plurality ofcolumns comprises a first plurality of cells, each of the firstplurality of cells being connected to a first bit line and a second bitline, and wherein each of the plurality of rows comprises a secondplurality of cells, each of the second plurality of cells of a row beingconnected to one of a plurality of word lines.

At block 520 of method 500, a plurality of first transistors (designatedas 312 a 1, 312 b 1, . . . , 312 n 1) are triggered to charge the firstbit line of a respective one of the plurality of columns to a firstpredetermined potential, each of the plurality of first transistors(designated as 312 a 1, 312 b 1, . . . , 312 n 1) are connected to thefirst bit line of the respective one of the plurality of columns. Atblock 530 of method 500, a plurality of second transistors (designatedas 312 a 2, 312 b 2, . . . , 312 n 2) are triggered to charge a secondbit line of the respective one of the plurality of columns to a secondpredetermined potential, wherein each of the plurality of secondtransistors (designated as 312 a 2, 312 b 2, . . . , 312 n 2) areconnected to the second bit line of the respective one of the pluralityof columns. At block 540 of method 500, a plurality of restorationcircuits (designated as 308 a, . . . , 308 m) are triggered to chargethe plurality of word lines (designated as WL1, . . . , WLm) to a thirdpredetermined potential, wherein each of the plurality of restorationcircuits (designated as 308 a, . . . , 308 m) are connected to one ofthe plurality of word lines (designated as WL1, . . . , WLm).

In accordance with example embodiments, a memory device comprises: acell array comprising a plurality of cells, each of the plurality ofcells operative to store a bit value; and a reset circuit connected tothe cell array, wherein the reset circuit is operative to reset, inparallel, the bit value stored in each of the plurality of cells to apredetermined bit value.

In example embodiments, a memory device comprises: a cell arraycomprising a plurality of cells, each of the plurality of cellsoperative to store one bit value; a power control circuit operative togenerate a first signal indicating an initiation of a power up durationof the plurality of cells and a second signal indicating a completion ofthe power up duration of the plurality of cells; and a reset circuitoperative to reset, in parallel, the bit value stored in each of theplurality of cells to a predetermined bit value during the power upduration.

In accordance with example embodiments, a method of resetting a memorydevice comprises: generating a reset signal as a logical disjunction ofa first signal indicating an initiation of a power up duration of aplurality of cells and a second signal indicating a completion of thepower up duration of the plurality of cells of a memory device; andtriggering, through the reset signal, a reset of a bit value stored ineach of a plurality of cells of a cell array of a memory device to apredetermined bit value in parallel during the power up duration.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A memory device comprising: a cell arraycomprising a plurality of cells, each of the plurality of cellsoperative to store a bit value; and a reset circuit connected to thecell array, wherein the reset circuit is operative to reset, inparallel, the bit value stored in each of the plurality of cells to apredetermined bit value, wherein the reset circuit comprises a resetsignal generator circuit operative to generate a reset signal, andwherein the reset signal is operative to trigger resetting, in parallel,of the bit value stored in each of the plurality of cells to thepredetermined bit value.
 2. The memory device of claim 1, wherein theplurality of cells are arranged in a matrix of a plurality of rows and aplurality of columns, wherein each of the plurality of columns comprisesa first plurality of cells, each of the first plurality of cells beingconnected to a first bit line and a second bit line, and wherein each ofthe plurality of rows comprises a second plurality of cells, each of thesecond plurality of cells of a row being connected to a word line. 3.The memory device of claim 2, wherein the reset circuit is operative toreset each of the plurality of cells to the predetermined valuecomprises the reset circuit being operative to charge the first bit lineof each of the plurality of columns to a first predetermined potential,the second bit line of each of the plurality of columns to a secondpredetermined potential, and the word line of each of the plurality ofrows to a third predetermined potential.
 4. The memory device of claim1, wherein the reset circuit further comprises a plurality of biascircuits and a plurality of restoration circuits, wherein the resetsignal being operative to trigger the resetting, in parallel, of the bitvalue stored in each of the plurality of cells to the predetermined bitvalue comprises the reset signal being operative to: trigger each of theplurality of bias circuits to charge the first bit line of a respectiveone of the plurality of columns to the first predetermined potential andthe second bit line of the respective one of the plurality of columns tothe second predetermined potential, and trigger the plurality ofrestoration circuits to charge the word line of each of the plurality ofrows to a third predetermined potential.
 5. The memory device of claim4, wherein each of the plurality of bias circuits comprises a firsttransistor operative to charge the first bit line of the correspondingone of the plurality of columns to the first predetermined potential anda second transistor operative to charge the second bit line of thecorresponding one of the plurality of columns to the secondpredetermined potential.
 6. The memory device of claim 4, wherein eachof the plurality of restoration circuits comprises an invertor and aNAND logic gate, wherein an input of the NAND gate is connected to arespective output of a decoder circuit and an output of the invertor isconnected to a first input of the NAND gate, and wherein the resetsignal is provided to a second input, and wherein an output of the NANDgate is connected to the word line.
 7. The memory device of claim 1,wherein the reset signal generator circuit being operative to generatethe reset signal comprises the reset signal generator circuit beingoperative to determine a logical disjunction of a first signal and asecond signal, the first signal indicating an initiation of a power upduration of the plurality of cells and a second signal indicating acompletion of the power up duration of the plurality of cells.
 8. Thememory device of claim 7, wherein the reset signal generator circuitcomprises an OR logic gate.
 9. A memory device comprising: a cell arraycomprising a plurality of cells, each of the plurality of cellsoperative to store one bit value; a power control circuit operative togenerate a first signal indicating an initiation of a power up durationof the plurality of cells and a second signal indicating a completion ofthe power up duration of the plurality of cells; and a reset circuitoperative to reset, in parallel, the bit value stored in each of theplurality of cells to a predetermined bit value during the power upduration.
 10. The memory device of claim 9, wherein the reset circuit isoperative generate a third signal, the third signal being operative totrigger the reset of the bit value stored in each of the plurality ofcells to the predetermined bit value during the power up duration. 11.The memory device of claim 9, wherein the reset circuit is operativegenerate the third signal comprises the reset circuit is operative togenerate the third signal as a logical disjunction of the first signaland the second signal.
 12. The memory device of claim 9, wherein thereset circuit being operative to reset the bit value stored in each ofthe plurality of cells to the predetermined bit value during the powerup duration comprises the reset circuit being operative to: determinethat a number of the plurality of cells is more than a predeterminednumber; and partition the plurality of cells in a first sub-block and asecond sub-block.
 13. The memory device of claim 12, wherein the resetcircuit being operative to: reset a first plurality of cells in thefirst sub-block in parallel; and reset a second plurality of cells inthe second sub-block in parallel.
 14. The memory device of claim 12,wherein the reset circuit further comprises a finite state machineoperative to indicate a status of reset of the first plurality of cellsin the first sub-block and reset of the second plurality of cells in thesecond sub-block.
 15. The memory device of claim 9, wherein the resetcircuit being operative to reset the bit value stored in each of theplurality of cells to the predetermined bit value during the power upduration comprises the reset circuit operative to reset the bit valuestored in each of the plurality of cells to a bit value zero during thepower up duration.
 16. The memory device of claim 9, wherein the powercontrol circuit is operative to generate a fourth signal prior to thefirst signal, wherein the fourth signal is operative to power up aplurality of peripheral components of the memory device.
 17. A method ofresetting a memory device, the method comprising: generating a resetsignal as a logical disjunction of a first signal indicating aninitiation of a power up duration of a plurality of cells and a secondsignal indicating a completion of the power up duration of the pluralityof cells of a memory device; and triggering, through the reset signal, areset of a bit value stored in each of a plurality of cells of a cellarray of a memory device to a predetermined bit value in parallel duringthe power up duration.
 18. The method of claim 17, wherein triggering,through the reset signal, the reset of the bit value stored in each ofthe plurality of cells of the cell array of the memory device to thepredetermined bit value in parallel during the power up durationcomprises triggering, through the reset signal, the reset of a bit valuestored in each of the plurality of cells of a cell array of the memorydevice to the predetermined bit value in parallel during the power upduration, wherein the plurality of cells are arranged in a matrix of aplurality of rows and a plurality of columns, wherein each of theplurality of columns comprises a first plurality of cells, each of thefirst plurality of cells being connected to a first bit line and asecond bit line, and wherein each of the plurality of rows comprises asecond plurality of cells, each of the second plurality of cells of arow being connected to one of a plurality of word lines.
 19. The methodof claim 18, wherein triggering, through the reset signal, the reset ofthe bit value stored in each of the plurality of cells of the cell arrayof the memory device to the predetermined bit value in parallel duringthe power up duration comprises: triggering a plurality of firsttransistors to charge the first bit line of a respective one of theplurality of columns to a first predetermined potential, each of theplurality of first transistors are connected to the first bit line ofthe respective one of the plurality of columns; triggering a pluralityof second transistors to charge a second bit line of the respective oneof the plurality of columns to a second predetermined potential, whereineach of the plurality of second transistors are connected to the secondbit line of the respective one of the plurality of columns; andtriggering a plurality of restoration circuits to charge the pluralityof word lines to a third predetermined potential, wherein each of theplurality of restoration circuits are connected to one of the pluralityof word lines.
 20. The method of claim 17, wherein triggering, throughthe reset signal, the reset of the bit value stored in each of theplurality of cells of the cell array of the memory device to thepredetermined bit value in parallel during the power up durationcomprises: determining that a number of the plurality of cells is morethan a predetermined number; partitioning the plurality of cells in afirst sub-block and a second sub-block triggering reset of a firstplurality of cells in the first sub-block in parallel; and triggeringreset of a second plurality of cells in the second sub-block inparallel.